1. Field of the Invention
This invention relates to a light collective optical system for light sources that has a wide divergence angle, and in particular, to a light collective optical system of a light source device used in an endoscope or a surgical microscope.
2. Description of Related Art
Recently, endoscopes have been widely used in which the internal organs are observed by inserting a slender insertion tube portion into a body or treatment tools inserted into a treatment tool channel are used when the necessity arises and thereby various treatments can be carried out. A conventional light source device used in such an endoscope is constructed so that a reflecting mirror is placed only behind a light source lamp, and direct light from the light source lamp and reflected light by the reflecting mirror are collected at the entrance end face of a light guide. In the conventional light source device, however, since the numerical aperture of the light guide is generally small, part of the direct light from the light source lamp is scattered to impair the efficiency of incidence on the light guide, and it is difficult to efficiently transmit the light from the light source lamp to the light guide.
Thus, in order to obviate such a defect, various light source devices shown in FIGS. 1A-1C are proposed (refer to, for example, Japanese Patent Kokai No. Hei 10-48539). In these figures, reference numeral 1 denotes a light source; 2, 3, 5, 6, and 8 denote reflecting mirrors; 6a denotes an aperture; 4 and 9 denote light guides; and 7 denotes a collective lens.